Apparatus for raising and lowering an off-shore platform



' Feb. 17, 1970- J. r-z. SUTTON APPARATUS FOR RAISING 11mm LOWERING ANOFF-SHORE PLATFORM R m N 1 w m t M T. w U h S cw Du S M N e w in J S 511 x hnnu m d IE/JII I I 2 I J 1 m 9 1 a ll I o I d m m E [I i FATTORNEYS v Feb. 17,1970 J R. SUTTON APPARATUS FOR RAISING AND LOWERINGAN OFF-SHORE PLATFORM Filed Oct. 26, 1967 3 Sheets-Sheet 2 FIG. 3

FIG. 2

INVENTOR JOHN R. SUTTON ATTORNEYS.

Feb. 17; 1970 .L'RLSUTTON I 3,495,306 APPARA US FOR RAISING AND LowERInGAN OFF-SHORE PLATFORM 3 Sheets-Sheet s FIG-4 I I H615 Filed Oct. 26,1967 INVENTOR JOHN R SUTTON ATTORNEYQ United States Patent 3,495,806APPARATUS FOR RAISING AND LOWERING AN OFF-SHORE PLATFORM John R. Sutton,1189 Calder Ave., Beaumont, Tex. 77701 Filed Oct. 26, 1967, Ser. No.678,397 Int. Cl. B66f 3/08 US. Cl. 254-107 14 Claims ABSTRACT OF THEDISCLOSURE An off-shore platform includes a horizontal deck supported ona plurality of legs extending vertically and sl1 1- ably through thedeck. At least one elevating assembly is associated with at least one ofthe legs for raising and lowering the deck relative to the leg. Theelevating assembly comprises first and second elevating units. Eachelevating unit includes a vertically extending structure fixedly securedto the deck and provided with guiding members. Connecting means adaptedfor selective connection to the legs are guided for vertical motionrelative to the structure by the guiding members between one positionadjacent the deck and another position adjacent an end portion of thestructure remote from the deck. Each elevating unit further includesmain moving means for selectively causing reltaive vertical motionbetween the structure and the associated connecting means in onevertical direction, and a return moving means for causing relativevertical motion in an opposite direction. The moving means of the firstand second elevating units are operatively interconnected so that themain moving means of the one elevating unit operates concurrently withthe return moving means of the other elevating unit. In operation, oneonly of the elevating units is engaged with the leg and the asosciatedmain moving means is operated to cause vertical movement of the deckalong the leg with the return moving means of the other elev ating unitoperating concurrently to return the associated connecting means toposition for commencement of the next succeeding vertical movement ofthe deck along the leg by the other of the elevating units.

The elevating assembly also includes locking means connected with thefirst and second elevating units for automatically locking eachconnecting means to its associated structure uopn failure of theasosciated main moving means, to provide a fail-safe capability.

Background of the invention This invention relates to apparatus forraising and lowering a platform of the type used for supportingequipment at variable heights above ground level such as, for example, atower for supporting geophysical, radio, radar, or nuclear equipment. Inparticular, but not exclusively, the invention relates to an off-shoreplatform for performing off-shore marine operations such as underwaterdrilling operations.

In performing elf-shore marine operations in continental shelf areas orthe like, it is sometimes advantageous to use an off-shore platform ofthe so-called jackup type for supporting oil drilling and likeequipment. Such jackup platforms usually comprise a horizontal decksupported on a plurality of legs which rest on the sea bed at theirlower ends and which extend vertically and slidably through the deck.Extensible jacks may be secured to one side of the deck. The remote endof each jack is provided with means for selective locking engagementwith at least one leg. Similarly, the deck is also provided with meansfor selective locking engagement to the legs. By engaging the remoteends of the jacks with the legs :and disengaging the deck and thencausing linear extension or extraction of the jacks, the deck may bemoved vertically along the leg. Representative examples of such offshoreplatforms are disclosed in US. Patents Nos. 3,082,607, 3,245,658 and3,282,565, issued to the present applicant.

Although elevating platforms of the type described are generallysatisfactory, certain operational disadvantages may be encountered. Forexample, in performing the elevating sequence described, it is usuallynecessary, once the deck has been elevated and resecured to the leg, toundergo a period of dwell while the jack is retracted to place it incondition for the next subsequent lifting operation. Such periods ofdwell, however, may involve an unacceptable loss of time, particularlyin conditions where frequent adjustment of height of the platform isnecessary.

Another serious problem is posed by the possibility of jack failurewhich may occur from time to time due to weakness of the jack or thefluid line connections or similar causes. Jack failure may permit thedeck to commence slipping down the leg and such motion once started isdifiicult to check immediately in view of the enormous loads involved.In this event, local buckling of the leg and the platform, or other evenmore serious consequences, both in terms of capital lost and possibleinjury to life and limb of those working on the platform may beincurred.

Summary of the invention It is therefore a general object of theinvention to provide apparatus for raising and lowering an off-shoreplatform intended to obviate or minimize problems of the type previouslydescribed.

It is a particular object of the invention to provide apparatus forraising and lowering an off-shore platform wherein the amount of dwelltime required between successive steps of vertical movement iseffectively minimized.

It is yet another object of the invention to provide apparatus forraisin and lowering an off-shore platform designed to have fail-safecapabilities so that alternative fixed support for the platform isprovided at any time that one of the elevating jacks should fail underload.

One preferred embodiment of the invention intended to accomplish atleast some of the foregoing objects includes an elevating assemblyintended to be utilized in conjunction with an off-shore platform of thetype including a generally horizontal deck supported on a plurality ofground-engaging, generally vertical, legs extending slidably through thedeck. The elevating assembly is associated with one of the legs forraising and lowering the deck relative to the leg and includes first andsecond elevating units. Each of the elevating units includes avertically extending structure adapted to be fixedly secured to the deckextending generally perpendicular therefrom, with an end portion of thestructure spaced fixedly and remotely from the deck. Each elevating unitalso includes connecting means adapted for selective connection to theleg at any of various points spaced vertically along the leg. Eachconnecting means is guided for vertical motion relative to itsassociated one of the structures between one position adjacent theremote end thereof and another position adjacent the deck, by guidingmembers forming a part of each structure. Each elevating unit furtherincludes a main moving means connected with the structure and theassociated connecting means for selectively causing relative verticalmovement between the structure and the connecting means in onedirection, and a return moving means for causing relative verticalmotion therebetween in an opposite vertical direction. The moving meansof the first and l6COI1d elevating units are operatively interconnectedto :ause operation of one of the main moving means of )ne of theelevatin units to occur concurrently with )peration of the return movingmeans of the other of the :levating units. In operation, one only of theelevating Jnits is engaged with the leg and the associated main novingmeans operated to cause vertical movement of Lhe deck along the leg.Concurrently, the returning mov- .ng means of the other elevating unitis returning the associated connecting means to position for commence-."nent of a succeeding vertical movement of the deck along the leg bythe other of the elevating units.

The main and return moving means of each elevating Jnit includes shaftmeans fixedly connected with the lsosciated connecting means extendingvertically therefrom. Hydraulic jack means is fixedly connected with theassociated structure and with the associated shaft means for moving theshaft means vertically relative to the structure.

In order to provide a fail-safe capability first and second lockingmeans are connected with the structures of said first and secondelevating units respectively, and with the respective shaft means of theelevating units. Each of the locking means is automatically operable tofixedly engage the associated shaft means with the structure uponfailure of the associated one of the hydraulic iack means. Thisautomatically prevents further relative motion between the associatedconnecting means and the deck. In this manner, runaway downward motionof the deck along the leg which might occur upon failure of a liftingjack under load is automatically prevented.

In one embodiment of the invention each shaft means includes a first rodfixedly connected with the associated connecting means extendingvertically toward the end portion of the adjacent structure and a secondrod fixedly connected with the connecting means extending verticallytoward the deck. The hydraulic jack means include a single-acting mainhydraulic jack fixedly connected with the remote end of the structureand connected with the first rod for selective extension thereofoutwardly of the first jack, to move the associated connecting meanstowards the deck, and a single-acting return hydraulic jack fixedlyconnected with the structure adjacent the deck and connected with thesecond rod for selective extension thereof outwardly of the returnhydraulic jack to return the connecting means vertically. The first andsecond locking means each include an axially extending threaded portionupon one of the associated first and second rods. Each locking meansfurther includes a nut threadedly engagin the threaded portion of theone rod with the nut rotatively mounted upon and fixedly connected withthe adjacent structure. Each nut is rotated by a nut motor connectedwith the nut for rotating the nuts synchronously with axial motion ofthe associated rod to permit axial motion thereof relative to theassociated jack. The nut motor is operatively connected with theassociated main hydraulic jack to automatically prevent further rotationof the nut upon failure of the main hydraulic jack, thus fixedlyengaging the connecting means with the structure to prevent furthermotion of the deck.

In a first alternative embodiment of the invention, a double-actinghydraulic jack is connected with one of the first and second rods forselective extension and retraction thereof with the second rod providedwith vertically spaced notched portions engaged by a spring-loadedratchet plunger fixedly secured to the structure. The ratchet plungerprevents relative vertical motion between the structure and theconnecting means in one vertical direction corresponding to downwardvertical motion of the deck relative to the leg, but permits relativevertical motion in an opposite vertical direction.

In a second alternative embodiment, otherwise similar to the firstalternative embodiment, the ratchet plunger locking arrangement isreplaced by a threaded peripheral portion on the other of the first andsecond rods threadedly engaging a power-driven nut connected with thestructure, with rotation of the nut being automatically terminated uponfailure of the hydraulic jack.

In a third alternative embodiment of the invention, otherwise similar tothe first alternative embodiment, the ratchet and plunger arrangement isreplaced by a threaded portion on the other of the first and second rodsengaging a ball nut fixedly and rotatively mounted on the structure. Theball nut is of such high efficiency as to be rotated relative to thestructure by axial motion of the rod. However, rotation of the nut maybe terminated by action of a power-operated brake connected with thenut, the brake being actuated automatically upon failure of thehydraulic jack.

The drawing Certain preferred embodiments of the invention areillustrated in the accompanying drawings in which:

FIGURE 1 is a partially sectioned, partially broken away, perspectiveview of a preferred embodiment of an apparatus for raising and loweringan off-shore platform according to the present invention;

FIGURE 2 is a side view, partially in cross-section, of an elevatingunit forming a part of the apparatus shown in FIGURE 1;

FIGURE 3 is a side view, partially in cross-section, of a firstalternative embodiment of the elevating unit forming a part of thepresent invention;

FIGURE 4 is a side view, partially in cross-section, of a secondalternative embodiment of the elevating unit forming a part of thepresent invention; and

FIGURE 5 is a side view, partially in cross-section, of a thirdalternative embodiment of the elevating unit forming a part of thepresent invention.

Detailed description Referring to FIGURE 1 of the drawings, a portion ofa conventional, jackup type off-shore platform suitable for elevation byan apparatus according to the present invention, is there shown. Theportion of the off-shore platform illustrated includes a verticallyextending, hollow, cylindrical leg projecting slidably and snuglythrough a portion of a generally horizontal deck 4.

An elevating assembly according to the present invention for moving thedeck 4 vertically along the leg 2 includes a plurality of separateelevating units 6, 8, 10 and 12 spaced at right angles about the leg 2.Each of the elevating units 6-12 includes a vertically extendingstructure 14. Each structure 14 includes a horizontal base 16 secured tothe deck, two spaced, opposed, vertically extending, side members 18 andan upper end member 22 secured to the upper ends of the two side members18 in fixed spaced relation above the base 16. Each of the elevatingunits 6-12 further includes a connection block 24 mounted for verticalmotion within and relative to the associated structure 14. The block 24is guided between the base 16 and the upper end member 22 by sidewardlydirected, vertically extending projections 26 on the connection block24, which snugly and slidably travel within opposed, inwardly facing,vertically extending guide channels 28 provided in each of the sidemembers 18. Each connection block 24 includes a conventional,selectively r actuated, motor operated plunger 30 of a type described inmore detail in applicants co-pending application Ser. No. 663,330, filedAug. 25, 1967. Each plunger 30 is movable radially towards the leg 2upon selective actuation to selectively engage the plunger 30 with anadjacent one of a plurality of vertically spaced apertures 31 providedin the leg, to fixedly engage the block 24 with the leg 2 againstvertical or radial motion. Local stiffening for the leg 2 in the regionof the apertures is provided by a vertically extending continuous strip32 fixedly connected to the exterior of the leg 2 and by localreinforcing plates 33 fixedly connected to the interior of the leg 2about each of the apparatus 31.

To move the connecting block 24 of each of the elevating units 612downwardly within the associated structure 14, each elevating unit isprovided with a single acting main hydraulic jack 36 secured to theupper side of the upper end member 22 of the structure 14. Each jack 36(FIGURE 2) includes a cylinder 37 having a closed upper end with apiston 38 slidably mounted in the cylinder. Fluid applied from aconventional source (not shown) through a connection 39 to the cylindermoves the piston 38 downwardly. The piston 38 is connected by a ram orrod 40 to the upper side of the adjacent connecting block 24 andapplication of fluid pressure to the hydraulic jack forces the rod 40downwardly to move the connection block 24 downwardly relative to thestructure 14.

To return the connecting block 24 from a final position adjacent thebase to a starting position adjacent the end member 22, a second rod orram 44 connected to the underside of the block 24 is moved upwardlyrelative to the structure 14 by another, generally similar,singleacting, return hydraulic jack 26 fixedly secured to the base 16and extending downwardly through the deck 4.

Suitable conventional hydraulic power and control equipment (not shown)connected with the plungers and the various jacks is provided foreffecting selectively controlled operation of the elevating units in themanner about to be described.

In operation, the elevating units are operated in pairs with the units 8and 12 constituting a first pair and the units 6 and 10 constituting asecond pair. Commencing an operating cycle with the units in thepositions shown in FIGURE 1, the plunger 30 of the first pair ofelevating units 8 and 12 are selectively engaged with the adjacentapertures 31 in the legs to fixedly connect the first pair of elevatingunits 8 and 10 with the leg 2. At the same time, the plungers 30 of thesecond pair of elevating units 6 and 10 are selectively withdrawn fromthe leg. The main jacks 36 of the first pair of elevating units 8 and 10are then operated to extend the rams 40 thereby raising the structures14 relative to the associated connecting blocks 24 fixedly engaged withthe leg 2, thus raising the deck 4 along the leg 2. At the same time,the connecting blocks 24 of the second pair of elevating units 6 and 10are being returned to their starting position by concurrent operation ofthe associated return jacks 46 which are operatively interconnected withthe main jacks 36 of the first pair of elevating units and with thesource of fluid pressure by conventional hydraulic control circuitryeX-J tending the rams 44 to their upper position adjacent the endmembers 22 of the associated structures 14.

As the bases 16 of the first pair of elevating units 8 and 12 approachtheir associated connection blocks 24, the connection blocks 24 of thesecond pair of elevating units 6 and 10 are concurrently approaching theend members 22 of their associated structures 14. Operation of thevarious jacks 36 and 46 is then terminated with the plungers 30 of thesecond pair of jacks 6 and 10 aligned with the now adjacent ones of theapertures 31 and the plungers are operated to engage to fixedly securethe second pair of elevating units 6 and 10 to the leg. A second cycleof operation similar to that just described is then performed but withthe second pair of elevating units 6 and 10 functioning to elevate thedeck while the connecting blocks 24 of the first pair of elevating units8 and 12 are returned to their starting position for the next elevatingcycle by the first pair of elevating units.

Lowering of the deck is performed in a similar manner but with thedirections of travel reversed.

It will be appreciated that by operating the elevating units in tandemin this manner with one pair of elevating units being returned to itsstarting position while the other pair of elevating units isconcurrently raising the deck, the amount of dwell time between thesuccessive lifting cycles is substantially reduced and may in fact bealmost eliminated. In this manner, particularly rapid elevating ratesmay be achieved, thus rendering the plat form particularly suitable foroperations requiring frequent raising and lowering operations.

In a particular safety aspect of the invention intended to preventrun-away motion of the deck down the leg in the event that one of themain jacks 36 should fail while engaged in moving the deck under load,the ram 40 of the failed jack automatically becomes immediately lockedagainst further motion relative to the associated one of the structures14 upon failure. This function is effected in the preferred embodimentby providing the ram 40 with a threaded portion extending along itsexternal periphery and passing through a nut 48 in threaded engagementtherewith. The nut 48 is fixedly and rotatably mounted on the lower endof the main ram 36 and is provided with gear teeth on its peripherymeshingly engaging a second gear wheel 50 drivingly connected with amotor 52 fixedly connected with the structure 14. In normal operation,the motor 52 is power driven by conventional means (not shown) to permitthe ram 40 to move axially in and out of the jack 36. However, the fluidsupply to the ram 36 and the power connection to the nut motor 52 areoperatively interconnected so that a sudden drop in fluid pressure (suchas would be caused by failure of the hydraulic jack 36) terminates powerdrive to the motor 52 so that further motion of the nut 48 isautomatically prevented, thereby locking the ram 40 in its particularposition of extension. Such operative interconnection may be provided ina number of ways; for example, the nut motor 52 may be driven byelectrical or fluid power through a power circuit including a pressuresensitive switch responsive to fluid pressure in the main jack andopened by a spring upon fall in fluid pressure below operating level tobreak the power circuit to the nut motor. However, such a mode ofoperative interconnection is exemplary and other conventional forms ofoperative interconnection may be employed as desired. Thus, with theparticular connecting block 24 engaged with the leg 2 and with the ram40 locked against further movement relative to th jack 36 and thestructure 14 by the nut 48, further relative motion between the deck 4and the leg 2 is automatically prevented to provide a fail-safecapability.

In the preferred embodiment, a commercially available threaded ram jackmanufactured by William S. Pine Company, Los Angeles, Calif, whichincludes the hydraulic jack 36, the threaded ram 40, the threaded nut48, and nut motor 52, is utilized. However, it will be appreciated thatother forms of jack having the construction described including athreaded ram, a nut engaging the ram and a motor for turning the nutwith the motor automatically rendered inoperative upon failure of thejack may be utilized.

In a first alternative embodiment of the invention shown in FIGURE 3,each of the previous described elevating units 6-12 is provided with adouble acting hydraulic jack 66 in place of the single acting hydraulicjack 36 provided in the preferred embodiment. Each double acting jack isof conventional form having a piston 62 movably mounted within acylinder 63 with fluid connections 64 and 66 to the cylinder 63 atopposite ends thereof for selective application of fluid under pressureselectively moving the piston 62 in one axial direction or the other inthe jack. The piston 62 is connected by a plain rod or ram 68 to theupper side of the previously mentioned connecting block 24 which may bemoved upwardly or downwardly relative to the associated structure 14from the starting position adjacent the end member 22 to the finalposition adjacent the base 16.

To provide a fail-safe capability for the first alternative embodiment,a second rod 70 fixed to the underside of the connecting block 24 by apivotal connection 72 and eX- tending downwardly is provided. The rod 70extends slidably into a vertically extending passage 73 passing throughthe previously mentioned base 16 and the deck 14. On its externalperiphery facing away from the leg 2, the rod 70 is provided with aplurality of vertically spaced ratchet notches 72 each of which isdefined by a horizontal, radially extending lower edge 74 and anupwardly and radially outwardly inclined upper edge 76. Slidably mountedin a bore 74 provided in the base 16 is a horizontal ratchet plunger 78provided with a forward end 80 configured to matingly engage the slots72 of the rod 70 one at a time. The ratchet plunger 78 is biased intoengagement with the rod 70 by a compression spring 82 surrounding aportion of the plunger 78 and extending between an abutment 84 on theplunger 78 and a fixed plate 86 secured to the base 16. In operation,with the associated connecting block 24 engaged with the leg, as shownin FIGURE 3, and with the hydraulic jack 60 having fluid applied theretothrough the port 64 to extend the ram 68 downwardly to elevate the deck4 along the leg, the inclined faces 76 of the notches 72 will be movingdownwardly relative to the plunger 78 which is successively depressedtopermit downward movement of the rod 70. If, however, the hydraulicjack 60 should fail, downward movement of the deck 4 relative to the leg2 would be prevented by engagement of the horizontal lower face of theforward end 80 of the plunger 78 with the horizontal lower edge 74 ofthe particular notch 72 currently engaged by the plunger, to providefail-safe capabilities.

In order to enable the jack 60 to return the connecting block 24 to thestarting position when necessary, conventional means such as anelectrical solenoid (not shown) attached to the plunger 78 are actuatedto withdraw the plunger completely from contact with any of the notches72 in the rod 70.

It will further be noted that in order to provide additional rigidityfor the various elevating units 6-12 an annular box member 90 extendingabout the leg 2 and connected with each of the end members 22 of theseparate elevating units 6-12 is provided. The box member 90 is fixedlyconnected with the deck by four, rigid, similar, vertically extendingsupport members 92 each of which is positioned adjacent one of theelevating units 6-12. The box member 96 includes two opposed annular,horizontally extending, upper and lower plates 94 and 96 with the lowerplate 94 fixedly secured to the upper sides of the previously mentionedend members 22 of the elevating units 612. The plates 94 and 96 areconnected together at their inner ends by a peripherally extendingvertical web 98 extending about and spaced from the leg 2 and at theirouter ends by portions of the various supports 92.

It will be appreciated that this additional structure comprising the boxmember 90 and the supports 92 provide substantial extra rigidity andbracing for the various elevating units and may also be provided for thepreferred embodiment previously described and for each of the otherembodiments shortly to be described.

In a second alternative embodiment of the invention wherein eachelevating unit is provided with a double acting hydraulic jack 60 in amanner similar to that of the first alternative embodiment, dependingthreaded rods 120 are secured one each to the undersides of the variousconnecting blocks 24 by a pivotal connection 122. Each rod 120 extendsvertically downwardly and is provided in the place of the ratchet rod 70of the first alternative embodiment. The threaded rod 120 threadedlyengages a threaded nut 124 rotatably and fixedly connected with theadjacent base 16 of the associated structure 14. The nut 124 is providedwith a tooth periphery meshingly engaging a gear wheel 126 driven by amotor 128 fixedly connected with the structure 14. The rod 120 extendsdownwardly of the nut 124 into suitably located vertically extendingpassages provided in the base 16 and deck 4 in order to permit thepassage therethrough of the rod 120 as the rod moves downwardly. The nutmotor 128 drives the nut in the manner previously described for thefirst embodiment to permit vertical motion of the rod relative to thenut. However, the power supply (not shown) to the motor 128 isoperatively interconnected (as previously described for the preferredembodiment) with the fluid supply to the hydraulic ram 60 in such amanner that upon failure of the ram the nut becomes automatically lockedagainst rotation to prevent further vertical motion of the rod 120, thuspreventing motion of the deck down the leg.

The threaded rod 120, nut 124 and nut motor 128 form part of anotherhydraulic threaded ram unit of the type previously described for thepreferred embodiment but with the hydraulic connections to the ramplaced in a disconnected or inoperative condition. However, it will beappreciated that any power driven nut with the motor driving the nut andoperativey connected with the source of fluid to the main hydraulic ram60, may be provided.

A third alternative embodiment of the invention illustrated in FIGURE 5is similar to the first and second alternative embodiments in that thevarious connection blocks 24 are each moved by separate double actinghydraulic jacks 60 connected to the associated upper end members 22 ofthe structure of the various elevating units 612. However, one of aplurality of depending threaded rods 138 is connected to the undersideof each connecting block 24 by a gimbal connection 140 permittingpivotal movement of the rod 138 relative to the associated connectingblock 24 about two mutually perpendicular horizontal axes. A flexible,bellows type, protective sleeve 142 is provided between each gimbalconnection 140 and the base end 16 of the associated structure 14 toprevent corrosion of the threaded rod 138 by sea spray and the like.

Each of the rods 138 passes through and threadedly engages an associatedball nut 142 rotatably and fixedly mounted within conventional thrustbearings, generally designated 144, mounted in the adjacent base 16. Asthe advantages of ball nuts and their construction and operation aregenerally well known, further description of the details of the ball nut142 will not be given except to say that it may be of the typedisclosed, for example, in US. Patent No. 2,932,209.

The ball nut 142 is of such high screw efliciency that in normaloperation axial motion of the threaded rod 138 relative to the ball nut142 is not prevented by the ball nut 142 but instead causes rotationthereof in the bearings 144 about the vertical axis of the rod 138.Fixedly secured to the exterior of the ball nut 142 is a horizontallydisposed peripherally extending bevel gear 146 meshingly engaging asecond bevel gear 148 connected to one end of a horizontally disposedshaft 150 mounted for rotation about a horizontal axis in the base 16.Secured to the other end of the shaft 150 is a power operated brake 152fixedly connected with the structure 14 and in a disengaged positionfrom the shaft 150, permitting free rotation thereof. However,the powersupply to the brake 152 is operatively interconnected with the fluidsupply to the double acting hydraulic ram 60 (by conventional means suchas those previously discussed for the preferred embodiment) so that uponfailure of the ram 60 the brake 152 is automatically applied to theshaft 150 to prevent rotation thereof relative to the adjacent structure14. Braking of the shaft 150 prevents rotation of the ball nut 142 sothat further vertical motion of the rod 138 is arrested thus preventingfurther vertical motion of the deck relative to the leg.

It will be appreciated that in constructing an apparatus for raising andlowering an off-shore platform according to the present invention,certain important advantages are provided.

Particularly significant is the use of elevating units operating intandem so that first one elevating unit is engaged with the leg andoperated to elevate the deck while the other of the elevating units isdisengaged from the leg and is concurrently placed in condition readyfor the commencement of the next succeeding elevating step. In

this manner, dwell time between successive elevations of the deckrelative to the platform is minimized, thereby providing for enhancedrates of deck travel.

Further, important advantages are provided by the failsafe capabilityincluded in each of the several embodiments of the invention. Forexample, the provision of a threaded ram and power driven nut providedin the preferred embodiment ensures that the deck becomes automaticallylocked to the engaged connecting block if at any time one of the mainjacks moving the deck should fail.

A similar function is provided by the ratchet plunger of the secondembodiment, by the threaded ram of the third embodiment and by the ballnut and power brake of the fourth embodiment.

Although the invention is described with reference to certain preferredembodiments, it will be apparent to those skilled in the art thatadditions, deletions, modifications, substitutions, and other changesnot specifically described or illustrated in the embodiments describedmay be made within the purview of the appended claims.

I claim:

1. In an off-shore platform including a generally horizontal decksupported on a plurality of ground-engaging generally vertical legsextending slidably through the deck, at least one elevating assemblyassociated with at least one of the legs for raising and lowering thedeck relative to the leg, said elevating assembly comprising:

first and second elevating units, each of said first and secondelevating units including,

connecting means adapted for selective connection to the leg at any ofvarious points spaced vertically along the leg,

a vertically extending structure adapted to be fixedly secured to thedeck extending generally perpendicularly therefrom, said structureincluding,

an end member remote from the deck,

guiding members for contacting and guiding said connecting means forvertical motion thereof relative to said structure between one positionadjacent said end member and another position adjacent the deck;

main moving means connected with said structure and with said connectingmeans for selectively causing relative vertical movement between saidstructure and said connecting means in one vertical direction;

return moving means connected with said structure and with saidconnecting means for selectively causing relative vertical movementbetween said structure and said connecting means in an opposite verticaldirection to said one direction;

said moving means of said first and second elevating units beingoperatively interconnected to cause operation of said main moving meansof one of said elevating units to occur concurrently with operation ofsaid return moving means of the other of said elevating units,

whereby during vertical movement of the deck along the leg with one onlyof said elevating units engaged with the leg, said connecting means ofthe other of said elevating units is concurrently returned to positionfor commencement of a succeeding vertical movement of the deck along theleg by the other of said elevating units.

2. An elevating assembly as defined in claim 1 wherein,

said main and return moving means of each of said elevating unitsinclude,

shaft means fixedly connected with the associated said connecting meansextending vertically therefrom, and

hydraulic jack means fixedly connected with said structure and connectedwith said shaft means for moving said shaft means vertically relative tosaid structure.

3. An elevating assembly as defined in claim 2 further including,

first and second locking means connected with said structures of saidfirst and second elevating units respectively and with the respectivesaid shaft means of said elevating units, each of said locking meansautomatically operable to fixedly engage the associated said shaft meansand said structure upon failure of the associated one of said hydraulicjack means,

whereby further relative motion between the leg and the deck isautomatically prevented.

4. An elevating assembly as defined in claim 2 wherein,

each said shaft means includes,

a first rod fixedly connected with the associated one of said connectingmeans extending vertically toward said end member of the adjacent saidstructure, 1

a second rod fixedly connected with the associate one of said connectingmeans extending vertically toward the deck;

each said hydraulic jack means including,

a single acting, main hydraulic jack fixedly connected with said endmember of the associated said structure and connected with theassociated said first vertical rod for selective extension thereofoutwardly of said first jiack,

a single acting, return hydraulic jack fixedly connected with theassociated said structure adjacent the deck and connected with theassociated said second rod for selective extension thereof outwardly ofsaid second hydraulic jack;

first and second locking means connected with said first and secondelevating units respectively, each said locking means including,

an axially extending threaded peripheral portion on at least one of theassociated said first and second rod-s,

a nut, threadedly engaging said threaded portion of said one rod, saidnut being rotatively mounted upon and fixedly connected with theadjacent said structure, and

a nut motor connected with said nut and with the adjacent said structurefor rotating said nut to permit axial motion of said one rod relative tosaid structure, saidnut motor operatively connected with the associatedsaid main hydraulic jack to automatically prevent further rotation ofsaid nut upon failure of said main hydraulic jack.

5. An elevating assembly as defined in claim 2 wherein each said shaftmeans includes,

a first rod fixedly connected with the associated one of said connectingmeans extending vertically towards said end member of the adjacent saidstructure,

a second rod fixedly connected with the associated one of saidconnecting means extending vertically towards said deck;

each said hydraulic jack means including,

a double acting hydraulic jack fixedly connected with said structure andwith one of said first and second rods for selectively extending andretracting said one of said rods outwardly and inwardly of said jack;and

first and second locking means connected with said first and secondelevating units respectively, each said locking means including,

engaging means fixedly connected with each of said structures forautomatically fixedly engaging therewith the associated other of saidfirst and second rods upon failure of the associated said hydraulic jackto prevent further relative motion between the associated saidconnecting means and the deck.

'6; An elevating assembly as defined in claim wherein, each saidengaging means includes,

vertically spaced, notched portions in said other rod of said first andsecond rods,

a spring-loaded, ratchet plunger fixedly secured to said structure, saidplunger engaging one of said notched portions at a time, said plunger inan engaged position with an adjacent notched portion preventing relativemovement between said structure and said connecting means in saidopposite direction, but permitting relative motion in said onedirection; and

means for selectively moving said plunger to an inoperative position outof contact with said notched portions.

7. An elevating assembly as defined in claim 5 wherein, each saidengaging means further includes,

an axially extending, threaded peripheral portion on said other rod ofsaid first and second rods,

a nut rotatively and fixedly connected with adja cent said structure,said nut threadedly engaging said threaded peripheral portion of saidother rod, and

a nut motor connected with said nut with adjacent said structure forrotating said nut to permit verical motion of said other rod relative tosaid structure, and nut motor operatively connected with the associatedsaid hydraulic jack to automatically prevent rotation of said nut uponfailure of said hydraulic jack.

8. An elevating assembly as defined in claim 5 wherein, each saidengaging means further includes,

an axially extending threaded peripheral portion on said other rod ofsaid first and second rods,

a ball nut rotatively mounted and fixedly connected with said structure,said ball nut threadedly engaging said threaded peripheral portion ofsaid other rod, said ball nut being of such high efficiency as to berotated by axial motion of said other rod through said ball nut,

a shaft fixedly connected with and rotatively mounted on said structure,

gear means drivingly connecting said ball nut and said shaft, and

a power operated brake connected with said structure and with saidshaft, said power operated brake operatively connected with theassociated said hydraulic jack to automatically prevent rotation of saidshaft upon failure of said jack.

9. In an off-shore platform including a generally horizontal decksupported on a plurality of ground-engaging,

generally vertical legs etxending slidably through the deck, at leastone elevating unit associated with at least one of the legs for raisingand lowering the deck relative to the leg, said elevating assemblycomprising:

connecting means adapted for selective connection to the leg at any ofvarious points spaced vertically along the leg,

a vertically extending structure adapted to be fixedly secured to thedeck extending generally perpendicularly therefrom, said structureincluding,

an end member remote from the deck,

guiding members for contacting and guiding said connecting means forvertical motion thereof relative to said structure between one positionadjacent said end member and another position adjacent the deck;

shaft means fixedly connected with said connecting means extendingvertically therefrom,

hydraulic jack means fixedly connected with said structure and connectedwith said shaft means for moving said shaft means vertically relative tosaid structure; and

locking means connected with said structure and with said shaft means,said locking means automatically operable to fixedly engage said shaftmeans and said structure upon failure of said hydraulic jack means toprevent further relative motion between said connecting means and thedeck.

10. An elevating assembly as defined in claim 9 wheresaid shaft meansfurther includes,

a first rod fixedly connected with said connected means extendingvertically towards said end portion of said structure,

a second rod fixedly connected with said connecting means extendingvertically toward the deck;

said hydraulic jack means including,

a single acting, main hydraulic jack fixedly connected with said endmember of said structure and connected with said first vertical rod forselective extension thereof outwardly of said first jack,

a single acting, return hydraulic jack fixedly connected with saidstructure adjacent the deck and connected with said second rod forselective extension thereof outwardly of said second hydraulic jack; and

locking means connected with said structure, said locking meansincluding,

an axially extending, threaded peripheral portion upon at least one ofsaid first and second rods,

a nut, threadly engaging said threaded peripheral portion of said onerod, said nut being rotatively mounted upon and fixedly connected withsaid structure, and

a nut motor connected with said nut sand sai-d structure for rotatingsaid nut synchronously with axial motion of said rod to permit movementthereof relative to said jacks, said nut motor operatively connectedwith the associated said main hydraulic jack to automatically preventfurther rotation of said nut upon failure of said hydraulic jack.

11. An elevating assembly as defined in claim 9 wheresaid shaft meansincludes,

a first rod fixedly connected with said connecting means extendingvertically towards the end portion of said structure,

a second rod fixedly connected with said connecting means extendingvertically towards the deck;

said hydraulic jack means including,

a double acting hydraulic jack fully connected with said structure andwith one of said first and second rods for selectively extending andretracting said one of said rods outwardly and inwardly of said jack;and

engaging means fixedly connected with said structure for automaticallyfixedly engaging therewith the other of said first and second rods uponfailure of the associated one of said hydraulic jacks to prevent furtherrelative motion between said connecting means and the deck.

12. An elevating assembly as defined in claim 11 where- 13 means forselectively moving said plunger to an inoperative position out 'ofcontact with said notched portions. 13. An elevating assembly as definedin claim 11 Where- 1n said engaging means includes,

an axially extending threaded peripheral portion on said other rod ofsaid first and second rods,

a nut rotatively and fixedly connected With said structure, said nutthreadedly engaging said threaded peripheral portion of said other rods;and

a nut motor connected with said nut and with said structure for rotatingsaid nut to permit vertical motion of said other rod relative to saidstructure, said nut motor operatively connected with said hydraulic jackto automatically prevent further rotation of said nut upon failure ofsaid hydraulic jack.

14. An elevating assembly as defined in claim 11 Wheresaid engagingmeans includes,

an axially extending, threaded peripheral portion on said other rod ofsaid first and second rods,

a ball nut rotatively mounted and fixedly connected with said structure,said ball nut threadedly engaging said threaded peripheral portion ofsaid other rod, said ball nut being of such high efiiciency as to berotated by axial motion of said other rod through said ball nut,

a shaft fixedly connected with and rotatively mounted upon saidstructure,

gear means drivingly connecting said ball nut and said shaft; and

a power operated brake connected with said shaft, said power operatedbrake operatively connected with said hydraulic jack to automaticallyprevent rotation of said shaft upon failure of said jack.

References Cited UNITED STATES PATENTS 2,875,980 3/1959 Grace 92172,992,812 7/1961 Rasmussen 254107 3,083,592 5/1963 Carlstedt 92-173,090,360 5/1963 Bennett 254106 3,259,368 7/1966 Warnke 254-110 ROBERTC. R'IORDON, Primary Examiner D. R. MELTON, Assistant Examiner U.S. Cl.X.R.

